According to Phillips Industries, the December edition of its monthly Qwik Tech Tips newsletter outlines “in clear language” how best to troubleshoot trailer lights when they are not working properly.

This is the primary cause of trailer-light problems. Symptoms include flickering, fast-blinking, dimness, intermittent operation (often when a trailer ball is used for a ground), and complete failure.

Taillights get bounced around, dunked in the lake and soaked with road salt. So it’s no surprise that bulb filaments break and sockets corrode, causing a lot of lighting malfunctions. Sealed LED ...